Semiconductor substrates are used in a wide variety of applications. One such application is in the formation of micromechanical electrical system (MEMS) devices. As the need for increased complexity of the physical structure of MEMS devices has increased, a number of different shaping processes have been developed. Two major categories of shaping processes are bulk micromachining of silicon and surface micromachining. Each of these processes has unique benefits and capabilities.
Typically, the processes used in shaping a substrate allow for highly complex shapes to be defined in the plane of the substrate. These processes also allow for moving parts to be manufactured. One group of known components that incorporate moving parts are valves. One example of a micromachined valve is a thermally actuated microminiature valve having a seat substrate that is fabricated using a first semiconductor wafer. The seat substrate includes a flow via and a raised valve seat structure that surrounds the flow via at a front surface. A second semiconductor wafer is patterned to include a central armature for alignment with the raised valve seat structure and to further include an array of legs extending from the central armature. Each leg has two metallic layers, with each of the two metals having substantially different coefficients of thermal expansion. As the legs are heated, the difference in thermal expansion of the two metallic layers causes the legs to arch, thereby displacing the central armature relative to the flow via.
Whenever moving parts interact with other parts as in the valve described above, increased precision in manufacturing is required. The minimum achievable size for a particular component thus becomes a function of the uncertainties in semiconductor fabrication processes. Moreover, as the manufacturing processes become more complex for a given device, the failure rate of the device increases thereby increasing the cost of the devices. Additionally, mechanically actuated valves can be opened inadvertently, e.g., due to an external shock.
In some applications, a valve must be operated only once during the lifetime of the device. By way of example, a device configured to provide a predetermined dose of a substance to a patient may incorporate a stored dose within a chamber sealed by a valve which is opened to administer the dose. In sensor devices, the sensor may be positioned within an isolated chamber so as to extend the life of the device. When the device is then ready to be used, the chamber is opened to the environment that is to be monitored. In order to ensure that the single use valves will operate when needed, however, substantially the same precision when manufacturing the single use valve as is required when manufacturing a valve that is operated multiple times. Accordingly, size limitations, manufacturing complexities, and expense for a single use valve, i.e., a valve that is to simply be opened once and thereafter remain open, is on a par with size limitations, manufacturing complexities, and expense multiple use valves.
What is needed, therefore, is a single use valve that can be easily incorporated into a MEMS device or semiconductor device. A further need exists for a single use valve that allows for increased manufacturing tolerances without increased failure rates compared to known single use valves. A single use valve which does not include the same size limitations, manufacturing complexities, and expense as other single use valves would be beneficial. a single use valve which is not operated by mechanically moving parts would also be beneficial.